Review of the brainworx bx_refinement plug-in

By editorApril 10, 2015

PRODUCT REVIEW

Brainworx have gained a strong reputation for innovative mid-side audio processing and many mastering engineers use their comprehensive suite of plug-ins which offer innovative ways to process complex mixes.

The latest addition to their plug-in range is the bx_refinement M/S Harshness Control, or probably better described as ‘de-harshing’ as its primary function is to remove harshness from recordings without any other significant sonic impact.

The de-harshness function is built around a dynamic band-stop filter with a fixed mid band centre frequency which I measured at 3142Hz. This filter can be controlled in a number of novel ways to reduce harshness in the track being processed.

Bainworx suggest that the bx_refinement plug-in will be useful across complex mixes, both across the 2-buss and also in mastering applications, especially where an excess of mid band content is causing the mix to sound harsh and perhaps where individual elements of the mix are struggling to be heard in this crowded part of the mix spectrum. I’ll go through the bx_refinement features first and then we’ll have a listen to how it sounds in use.

Damping control

The Damping control allows the band-stop (or notch) depth to be varied from 0dB to 20dB around the fixed centre frequency. The cute glowing tube gives a useful visual indication of the filter’s action on the audio being processed.

Soft and Hard options set the character of the filter’s response.

With soft damping, the filter slope is less steep and appears constant irrespective of the amount of damping (band-stop depth) applied.

With hard damping, the steepness of the filter varies considerably with the amount of damping (or band-stop depth) applied. With 6db of damping applied, there is little difference between the soft (green trace) and hard (red trace) settings, as shown below.

However, increase the damping to 20dB and you can see that the hard option (red trace) has a significantly steeper filter slope than the soft option (green trace), so when set to hard option, the filter’s Q increases as the damping setting is increased, as shown below.

Dynamic Filter Control

While the preset filter settings are a useful start to de-harshing, the bx_refinement really gets interesting when dynamic filter control is brought into play. There are two ways to do this;

Switching in the Dynamics button adds an additional amount of damping which varies according to the peak level of the audio, so high level peaks get more mid frequency cut applied and lower level audio is ‘deharshed’ less. A ‘speed’ control allows you to vary how quickly the dynamic filtering reacts to incoming audio peaks, a bit like the attack time on a compressor. A bargraph meter shows how much filtering is being applied dynamically.

It’s important to note that this Dynamics mode works in tandem with the preset damping control, so you can mix the two filter effects together, which in practice works really well.

The second method of dynamically varying the filter depth is to switch to Oscillator mode. This in turn has two options. In Sync mode the filter depth varies with the tempo set in your DAW, so now you have a filter whose depth is varying up and down with the beat. You can even shift the accent of this filter modulation by dragging a little sine wave graphic on the control window to emphasis or de-emphasis specific rhythmic elements within the bar, e.g. a hi-hat. It’s a really cool effect and tracks the song’s beat very accurately.

Switching the duration to Free allows you to set the modulation effect of the filter in seconds.

Presence

To use another compressor analogy, now that you have dynamically reduced the mid frequency harshness of the audio, it might be necessary to dial a little bit of brightness back in. The presence control allows you to dial in up to ± 6dB of presence filter boost or cut which seems to start more or less at the same frequency as used for the de-harshness filter. I plotted the frequency response of the presence filter at the maximum 6db boost and cut (below).

Saturation

And having de-harshed the mid frequency response, you may want to add a different type of colour back in, so Brainworx have provided a dial-in Saturation control which is calibrated from 0 to 100%. I did a quick spectral analysis of a 1kHz test tone with Saturation set to 50%. At this setting, it generated third harmonic (at -25dB) and fifth harmonic (at -52dB) on top of the fundamental. You need to be careful how much to dial-in as it can get pretty grungy towards the higher settings as you head towards a soft clipping effect.

Mix

Just like parallel processing has become popular in compression, the bx_refinement allows you to mix the unprocessed and processed audio from 0 to 100% of each component. This allows you to heavily process the audio and then just mix in a small amount to the original mix. This opens up an enormous palette of sonic possibilities.

Mid or Mid+Side

As I said at the start of this review, Brainworx are experts in processing Mid/Side, so you have the choice to apply the processing to Mid only or Mid + Side. This opens up another whole range of sound options including another way to vary the stereo width by reducing relative mid frequency content in the mid signal.

If you are not familiar with M+S processing then Brainworx have a handy primer here or you can read my own tutorial on M/S here.

Solo Filter

When pressed, Solo Filter lets you hear only the frequencies being processed, so it’s a bit like the inverse of the harshness control. I used this a lot when deciding how to set each of the controls during use and I’ve included an audio sample below.

Time to put bx_refinement to use

As bx_refinement was designed to help de-harsh complex mixes, it seemed appropriate to try it out first across the 2-buss. I decided to put together a short riff with a really busy mid band, so I started with a nice funky drum loop, in went a couple of electric guitars panned hard left and right, bass guitar, a sampled keyboard and another sampled sequencer. Apart from some compression and eq on the bass guitar, I left everything else unprocessed so that the mid range is pretty congested as you can hear below.

First I set the ‘static’ damping to soft and dialled in -6dB of de-harshing. Then I dropped down to the dynamic filtering. With the speed set to 34%, I increased the range until it was peaking at a further 4dB of de-harshing.

The combination of static and dynamic filtering tamed some of the worst of the mid range and I ended up dialling back in around +4dB of presence just to readjust the tonal balance to taste. You can hear the result below.

I have normalised both versions to peak at -1dBFS, but in reality, the settings I used resulted in a very small change in mix level of around 0.5dB.

Next I thought to try the Sync’d Oscillator option instead of the level tracked dynamics. I set the duration to track on the beat at 1/1 and set the depth to 10.4dB. This was also a good opportunity to let you hear the Solo Filter monitoring function in operation so I first recorded the processed output with Solo Filter switched in. You can clearly hear the filter emphasising the beginning of each bar and then reducing through the bar’s duration.

Use on an individual track

Although I guess that most uses of bx_refinement will be across the mix buss during mixdown or mastering, I though it would be interesting to try it out on an individual track. So I popped an instance into the sampled keyboard synth from the riff as it sounded a bit strident in its raw form.

Alongside the audio processing facilities, the included toolbar is very flexible, allowing plug-in bypass, 32 steps of Undo/Redo and 4 snapshots. You can also copy and paste settings between instances of the plugin.

Digital processing has opened up a range of possibilities for both mixers and mastering engineers which would never be practical to achieve in the analogue domain. Brainworx have taken a very novel approach in its application of dynamic filtering with the bx_refinement plugin. It’s ability to de-clutter the mid band of stereo mixes, I found to be effective across a wide range of material. The control panel is well laid out and becomes quite intuitive to use after a short time. The filter mid frequency and slope characteristics are well chosen, and although you might wonder why a variable frequency hasn’t been offered, I found the combination of fixed center frequency, adaptive filter slopes and flexible modulation options more than enough to work with.

You may want to turn to a more sophisticated saturation plug-in for many applications but it was nice to see a basic saturation effect included within the plugin. The mix control (between processed and unprocessed audio) is really great and encourages you to experiment with some extreme control settings, which can be mixed in with the clean audio to create some great tones. And don’t forget to experiment with Mid + Side which I predict will get more and more popular as mixers get familiar with that method of audio processing. Mastering engineers have long since adopted M+S as a fundamental tool within their sound processing palette.

Many thanks to the Plugin Alliance for supplying the evaluation copy of bx_refinement.